Silikaatstructuren

Silikaatstructuren refer to the diverse arrangements of silicon and oxygen atoms that form the backbone of silicate minerals, the most abundant class of minerals in the Earth's crust and mantle. The fundamental building block of all silicate structures is the silicon-oxygen tetrahedron, often abbreviated as TO4. This unit consists of a central silicon atom covalently bonded to four oxygen atoms, arranged at the corners of a tetrahedron.

These tetrahedra can link together in various ways by sharing oxygen atoms. This sharing can occur at one corner (a single oxygen atom bridging two tetrahedra), two corners (two oxygen atoms bridging), three corners (three oxygen atoms bridging), or all four corners. The degree of oxygen sharing dictates the resulting silicate structure and its properties.

The simplest structures are isolated tetrahedra, found in nesosilicates (e.g., olivine). When tetrahedra share one oxygen atom, they form linear chains, characteristic of inosilicates like pyroxenes. Sharing two oxygen atoms leads to double chains, seen in amphiboles. Sharing three oxygen atoms creates rings (cyclosilicates, e.g., tourmaline) or sheet structures (phyllosilicates, e.g., micas and clays). When tetrahedra share all four oxygen atoms, they form three-dimensional frameworks, as in tectosilicates (e.g., quartz and feldspars). The specific arrangement of these linked tetrahedra influences the mineral's hardness, cleavage, density, and optical properties.